F IB E R F O R M F O R M E D O F C A R B O N F IB E R C O M P O S IT E

C O N C R E T E IS P O U R E D IN A N D T H E S E V O ID S A R E F IL L E D .

FABRIC FORMED CONCRETE MATS FOR EROSION

CONTROL SYSTEM INTRODUCTION: This is a technique in which fiber forms of nylon, composite fiber and other different

type of polymers are made in factory. Selection of the materials required for the

fabrication of forms depends upon the site conditions and durability aspect required of

the fabric form according to the need.

These fabric forms are fabricated in such a pattern that different packets are

interconnected to each other forming a continuous mat.

These fabric forms also contain capillary pores for reduction of uplift pressure.

These fabric forms are transported to the site, soil is compacted and leveled on site

and these mat of fabric forms are laid on the surface. After laying, concrete is poured

in these mats through concrete pump into the packets.

Flow of concrete within the mats takes place on its own. Fine aggregate concrete is

used with little higher w/c ratio.

Mats can be designed with different size and shapes ranging from

Average thickness of mat with concrete filled inside (from 56mm to 350mm)

Mass per unit area with concrete filled inside (from 121 kg/m2 to 661 kg/m2)

Concrete quantity required (from 16.6 m2/m3 to 3m2/m3)

C/C spacing (from 127mm to 406 mm)

CAPILLARY PORES

SOIL SAMPLEUP LIFT WATER PRESSURE

FABRIC FORM

G.LG.L

sectional elevation

Practical application of this fabric formed concrete

These fabric formed concrete has a wide variety of application such as follows:

Drainage ditches

Channels and canals

Streams, river, and bayous

Lakes and reservoirs

Coastal and intercostals shorelines

Jetties and groins

Dikes and levees

Dune protection

Beach renourishment

Seawall and bulkhead scour protection

Boat launching ramps

Wildlife crossings

Low-water stream, crossings

Embankments

Underwater pipeline

bridge abutments and piers

Check dams

Dams and spillways

Ponds and holding basins

Landfill caps

Down chutes

Water control structures

REDUCE UPLIFT PRESSURE: Unlike traditional method, fabrics formed concrete are manufactured with built in filter drains

that reduce the mean phreatic level and pore pressures within the underlying soil, and thus

provide for the relief of hydrostatic uplift pressure, increasing the system stability.

The groves seen within are pores which are prefabricated in

the fabric form for release of pore uplift pressure.

MANAGEMENT OF HYDRALIC FLOW: Fabric formed concrete can be constructed with deeply patterned surfaces. These patterns

create a high coefficient of hydraulic friction, which result in reduced flow velocity and

reduced wave run-up. These surface characteristics impart stability to the system by reducing

velocities and also mean that the designer can affect the flow characteristics of a channel,

creating the opportunity for an “engineered” hydraulic system. By choosing the correct style

of form, in-channel flow can be slowed, reducing downstream velocities and discharge

turbulence. Or a hydraulic-efficient, smooth form (such as uniform section) can be chosen to

maximize drainage from a given area.

These fiber form concrete creates interconnected, tubular

concrete elements that are separated by large, interwoven

fiber form. These tubular elements create two directional-

determined coefficients of hydraulic friction.

ADAPTATION TO SOIL CONTOURS: Filled-in-place forms accommodate uneven contours, cures, and sub grades at the time that

they are filled. Consequently, the soil and the concrete protection are in intimate contact,

reducing the chance of under scour. Some forms create discrete concrete units, attached to

each other with fabric perimeters and/or embedded cables. As a result, the concrete mats can

articulate to adapt to uneven settlement.

These are specially designed for adaptation of uneven soil

topography, these are also designed for plantation of

different varieties of plantation according to the

surrounding environment which may comprise of grass

and shrubs, the (X) marks shown in the figure indicated

those part of the fiber form in which concrete is not filled

and after concreting the fabric form on site, these parts

are teared open for growing plantation, seedlings.

EASE TO INSTALLATION: Fabric forms are delivered to the job site ready-to-fill and require no additional forming

materials. Installation consists of preparing the area, laying out the fabric forms, and filling

them with concrete through a small line concrete pump. Wood or steel forming is not

required. The fabric forms themselves assure that the concrete assumes the proper

configuration, contours, dimensions and thickness. These mats do not require steel

reinforcement or concrete finishing. A small crew can be installed without dewatering the

site.

SIMPLE JOB MOBILIZATION: Fabric forms are extremely lightweight, so they can be rapidly shipped anywhere in the

world. The weight component of a fabric-formed system, the fine aggregate concrete, is

readily available from concrete suppliers worldwide. Once the site is prepared, simple hand

tools and concrete pump are all that is needed to fill the forms. And in area with difficult or

restricted access, the concrete can be pumped to the forms as far away as 800 feet (250

meters). Because of the low mobilization costs, it is practical to install fabric forms on jobs as

small as a hundred square feet (10 square meters). Regardless of the job size, the ease of

mobilization and transportation and the reduced equipment and labor requirements mean that

the hob goes in faster and at less cost per square unit of protected area.

ENVIRONMENTAL COMPATIBILITY: Fabric forms are designed to provide the least possible environmental impact. The fabric used

in the forms allows excess mixing water to escape while retaining the cement solids, fine

aggregate, and sand. These fabric forms have been designed to provide defined areas that can

be cut out after installation so that native vegetation can be planted or seeded to create a more

natural appearance. More over this linings and mats are free of hazardous projections that

could endanger pedestrians, animal’s vehicles, or boats.

This is a picture where the fabric form is used; the photo graph

was taken 6 months later after construction. Grass and shrubs

have developed in such a way that it becomes hard to see the

underlying fabric formed concrete lining, thus this technique

provides hydraulic, ecological, and aesthetic features.

HIGH STRENGTH CABLE REINFORCED FABRIC FORM

CONCRETE MATS: Articulation block mats form cable-reinforced concrete block mattresses that resist erosive

force. They are often installed where fiber form concrete mats are exposed to attack by wave

action and are used to protect shorelines, canals, rivers, lakes, reservoirs, underwater

pipelines, bridge piers, and other civil and marine structures from propeller wash, ship wakes,

waves, currents, and high velocity flows. Articulation block fabric consists of series of

compartments linked by interwoven perimeters. Grout ducts interconnect the compartments.

High strength revetment cables are installed between and through the compartments and

grout ducts. Once filled, these mats become a mattress of pillow-shaped, rectangular concrete

block. The interwoven perimeters between the blocks serve as hinges to permit articulation.

The cables remain embedded in the concrete blocks to link the blocks together and facilitate

articulation.

PARA WEB SOIL RETENTION SYSTEM INTRODUCTION: It is a fast and economical method of building an earth retaining

structure in a variety of environments including industrial, highway, marine and river work

and is based on Websol system. WEBSOL-SYSTEM: This system is based upon the use of polyethylene encased

polyester fiber multicards which act as a frictional anchor under compacted earth fill and tied

with pre-cast reinforced concrete panels through anchor bars, in short it is based on use of

polymeric products to reinforce and control drainage of soils.

COMPONENTS OF WEBSOL SYSTEM (PARAWEB SYSTEM)

FACING PANELS: These are cladding units in precast concrete. Precast concrete facing

units are 2 m wide by 1.6 m high and are normally 160 mm thick. They are lightly reinforced

with mesh. Units incorporate attachment loops and two lifting lugs are cast into the top of

each unit for handling.

PARAWEB ANCHOR TIES: The straps comprise

polyester tendons encased in a polyethylene sheath,

and are manufactured in three grades 30, 50, 10

Grade Minimum

short term

Minimum

long term

Maximum

design loads

Nominal

width (mm)

Nominal

thickness

breaking

loads (kn)

breaking

loads (kn)

(kn) (mm)

30 30 22.5 7.5 85 2.2

50 50 37.5 12.5 90 3.5

100 100 75.00 25.0 90 6.6

HORIZONTAL JOINT FILLER: Horizontal joint filler is required to be used to

avoid damage of concrete during placing of panels and for proper sealing of horizontal joints

between precast panels. Normally resin bonded cork is used for this purpose. VERTICAL JOINT FILLER: To close the vertical joints between pre-cast facing

panels flexible closed cell expanded polyethylene foam strips of 254 mm x 25 mm are used, DOWEL RODS: Vertical polypropylene dowel rods are fitted in to the units shoulders to

guide for placement of subsequent layer of precast panels. Dowel rods are of 25 mm dia.

STEEL ‘S’ CLAMP: The connection between the straps is made easily

using the temporary mild steel ‘S’ clamp. DESIGN LIFE: If constructed in accordance with the guidelines as

suggested by British board of agreement for roads & bridges (1983), the

estimated design life for such structures is 120 years. EXCAVATION AND FOUNDATION

CONSTRUCTION: Excavation is required be done

to provide for nominal base, which may be stepped

wherever necessary in the longitudinal direction

depending upon the topography of the area. depth of

foundation below finish ground level at the foot of the

wall should not be less than 800 mm. the concrete facing

panels at the base of the wall shall be placed on a level

footing of PC concrete M-20 within the tolerance of + 5

mm of the top level. Footing should be cured for a

minimum of 7 days prior to placing the bottom

panels.

BACKFILL MATERIAL: Following grading limits have been defined for use of back fill soil;

Maximum particle size may be increase in accordance

with site requirements.

Compaction within end 2 meters should only be done

with a light manually controlled machine without any

vibration. No heavy machinery having weight more than

1000kg should be brought in the vicinity of the width.

Minimum density achieved by compaction should be

95% of the maximum dry density as per IS:2720 PART VIII.

BENEFITS:

The principal reinforcement element of the system of the system, being made of

polyester fibers covered with a polyethylene sheath, is absolutely corrosion free and

inert to chemical.

The use of polymeric rear anchors

provides additional safety to the structure

by providing passive resistance in addition

to the active resistance provided by the

friction between the backfill soil and the

strips, thus the failure stress of reinforced

soil will be more then that of unreinforced

as shown in figure.

The structure is rigid and hence difficult to

be pulled out because of its continuous length, as also is the case with the rear

anchors.

Sieve Size Percentage Passing

150 mm 100

90mm 85-100

10mm 25-100

600 microns 10-65

63 microns 0-8

The system is very flexible and especially suited for areas susceptible to seismic

conditions.

Owing to their flexibility and interlocking system, the structure is very well able to

adapt to differential settlements and yet maintain its integrity.

SPEED: The speed of construction is at least 5 times much higher as compared to

reinforced concrete walls. The average rate of construction for Para web walls in

typical conditions would be approximately 20Sq.m per location per day (i.e.5 to 10 m

wall length/day).

SIMPLICITY & APPEARANCE: only three

main components are

required: panels, frictional

anchors and soil.

Construction may be

carried out with unskilled labour & light plant & the walls can be cast in variety of

attractive paterns & colours

ECONOMY: cost comparison has been carried out with the websol construction on

approach walls of road over-bridge at phagwara. Four approach walls (two on either

side) with websol system have been constructed. Total length of each wall is 326 m

with height varying from 1.5 m to 9.0 m. imported ‘paraweb’ material has been used

for this purpose. Panel casting has been done at a separate yard about 15 km away

from the site of erection. Total cost incurred for all the four walls is Rs. 145.00 lacks.

Net saving over R.C.C. walls with same height and length works out to Rs. 162.00

lacks. Net saving over R.C.C. walls thus works out to the extent of 10.5 per cent.

It has been noticed that for a height up to 2.m websol construction is not

economical as compared to the R.C.C. walls. With subsequent increase in height,

saving is effected.

INSTALLATION:

Panels are transported from the casting yard to the site of work with the help of light crane or

by any other convenient method. Bottom row of panels which is always a half panel are

placed on the foundation beam. The majority of the panels in any wall are a standard t shape

in elevation with edges shaped to interlock each panel with those adjacent to it.

Each panel is joined with the other in the

recommended sequence of drawing but

without any filler in between in the bottom

layer so as to ensure the flow of percolated

rain water. Panels are placed in the

required place with an inclination of 1 in

150 toward inner side to compensate for

subsequent movement due to filling

operations. Panels are temporarily

supported with the help of steel struts from outside to keep them in position with the fill

pressure is fully taken by ‘paraweb’ strips. Fill is then placed in layers with at least 95 percent

compaction leaving end 60cms near the panel where filler material is placed simultaneously.

Fill and filter material is brought to the level of first layer of frictional anchor. Paraweb layer

is then placed in position. Paraweb reinforcement is placed to the alignment shown in the

drawing in horizontal layers. It is looped between panel anchors and outer fixing bar. The

ends of paraweb are sealed using bitumen based sealant and at least 2 m overlap is provided

by means of a temporary wooden buckle. After laying each anchor, layer is hand tightened to

remove any slack before placing of filter materials. As fill

reaches top row of panels, next row of panels with the help

of plastic dowel rod (to be used as guidance) is placed by

maintaining line and level. At the top of first panel resin

bonded cork is placed which works as horizontal joint filler.

Plastozote foam is placed in the vertical joints to ensure the

joints to be watertight so that percolated rain water out

flows only through bottom layer. Sequence is then repeated till desired height is achieved.

Top panels are covered by casting in-suit caping beam to ensure one mass behavior of panels.

MECHANICAL PROPERTIES: (1) TENSILE STRENGTH: minimum long term breaking

loads of paraweb multicords after application of factor of

safety are given in figure:

(2) MODULUS OF ELASTICITY: short term stress/strain

graph is shown actual strain at break is app 0.6% after one

year with zero increase thereafter.

(3) EFFECT OF TEMPERATURE: mechanical properties of

geostrip vary very little within the temperature of -20o to + 65o C

(4) EFFECT OF WATER: there is no significant loss in strength when ‘paraweb’ is

immersed in water with ends sealed. Long term strength takes into account the effects

of hydrolysis due to local drainage.(i.e. dehydration)

(5) COEFFICIENT OF FRICTION: the coefficient of friction between paraweb and

the fill can be obtained from shear box tests conducted during execution.

(6) The black grade of polyethylene used as a protective sheath of paraweb multicord

suffers no deterioration from normal exposure to sunlight or from burial under wet

soil conditions.

(7) Paraweb has very good resistance to biodegradation.

(8) The principal of dehydration of paraweb polyester fibers is water.